This invention relates to a method for the avoidance of browning of a food product comprising a source of amino acids and carbohydrates, and more particularly at least one free carbonyl group. This invention also relates to a food product which does not brown in the course of time.
A method for the preparation of soy sauce, by the fermentation of a koji, hydrolysis of the fermented koji, the addition of sodium chloride so as to obtain a moromi, followed by fermentation of the moromi, is known for example from European Patent No. 417481. A fermented soy sauce of a dark brown colour, which can be dried and stored for a long period, is obtained by pressing after pasteurisation and clarification of the pressed juice.
The dark brown colour of soy sauce is partly due to the Maillard reaction, a reaction which takes place when a mixture comprising amino acids and carbohydrates, containing at least one free carbonyl group, is treated with heat, for example by drying. The rate of browning of the material, and the colour obtained, depends mainly on the operating conditions, namely the temperature and the duration of the heat treatment.
In order to avoid such browning of the material during heat treatment, it is possible to control the temperature and duration of the reaction, and to stop it before the colour becomes too dark. This is., however, to the detriment of the flavour which is unable to develop completely.
It has been proposed, in Japanese Patent JP 57100177, that a colouring-inhibiting agent comprising at least one calcium salt, preferably calcium chloride, should be added to the mixture of amino acids and carbohydrates before the reaction. The mixture obtained is then less susceptible to browning, by the Maillard reaction, during subsequent heat treatment.
Another method for the avoidance of the browning of a product in the course of its preparation has been proposed by Canadian Patent No. 850 600, and consists of adding an organic compound, which is capable of hydrolysis in contact with water, to the mixture of amino acids and carbohydrates. The product obtained then retains its initial colour for at least 4 days' storage at 55.degree. C., followed by 1 day at 90.degree. C.
These various processes avoid, to some extent, the appearance of a dark brown colour, by the Maillard reaction, on heat treatment, during preparation of the final product.
However, when these food products have a high concentration of reducing sugars, as is the case, for example, in soy sauces and flavouring agents based on soya, these sugars can react during the product drying stage, and even in the course of storage, and alter the organoleptic qualities of the product, developing an undesirable dark colour and possibly a caramel taste.